Handle false positive italics across list items

Simply checking for `markdown-list-face` in the potential italic range
seems to be a safer and more general approach.  It also covers the
hanging list test case in 6aafece and is more efficient since we've
already done the hard work of parsing the nested lists.

Also, remove an ambiguous test case. With the example below, Markdown.pl
does indeed generate a list item with italics:

* foo_bar
foo_bar

markdown-mode.el

@@ -2434,15 +2434,6 @@ Return nil otherwise."
                           (match-beginning 5) (match-end 5)))
     (goto-char (1+ (match-end 0)))))
 
-(defun markdown-list-p (pos)
-  (save-excursion
-    (goto-char pos)
-    (goto-char (line-beginning-position))
-    (looking-at-p markdown-regex-list)))
-
-(defun markdown-same-line-p (pos1 pos2)
-  (= (markdown-line-number-at-pos pos1) (markdown-line-number-at-pos pos2)))
-
 (defun markdown-match-italic (last)
   "Match inline italics from the point to LAST."
   (let ((regex (if (eq major-mode 'gfm-mode)
@@ -2453,11 +2444,11 @@ Return nil otherwise."
          ((markdown-range-property-any
            begin end 'face (list markdown-inline-code-face
                                  markdown-bold-face
+                                 markdown-list-face
                                  markdown-math-face))
           (goto-char (1+ (match-end 0)))
           (markdown-match-italic last))
-         ((or (markdown-same-line-p begin end)
-              (not (or (markdown-list-p begin) (markdown-list-p end))))
+         (t
           (set-match-data (list (match-beginning 1) (match-end 1)
                                 (match-beginning 2) (match-end 2)
                                 (match-beginning 3) (match-end 3)

tests/markdown-test.el

@@ -1743,7 +1743,6 @@ the opening bracket of [^2], and then subsequent functions would kill [^2])."
 
 (ert-deftest test-markdown-font-lock/italics-6 ()
   "Test multiline italics across list items."
-  :expected-result :failed
   (markdown-test-string
    "* something about function foo_bar
 * something else about foo_bar"
@@ -1760,12 +1759,6 @@ the opening bracket of [^2], and then subsequent functions would kill [^2])."
    "foo_bar
 * foo_bar"
    (markdown-test-range-has-face 4 7 nil)
-   (markdown-test-range-has-face 11 14 nil))
-
-  (markdown-test-string
-   "* foo_bar
-foo_bar"
-   (markdown-test-range-has-face 6 9 nil)
    (markdown-test-range-has-face 11 14 nil)))
 
 (ert-deftest test-markdown-font-lock/italics-after-hr ()